Arrhythmias – Supraventricular Tachycardia (SVT) – AVRT and AVNRT

Question 1

What does AVRT stand for?

Answer 1

Atrioventricular Re-entrant/Reciprocating Tachycardia

Question 2

What is AVRT?

Answer 2

a form of supraventricular tachycardia which presents in patients as occasional brief episodes of rapid heart contractions

Question 3

What is the rate of AVRT when there is rapid heart contractions?

Answer 3

150 – 250bpm

Question 4

What is AVRT caused by?

Answer 4

by the presence of abnormal accessory pathways that allow the impulse to travel in a loop between the atria/ventricles

Question 5

What is the onset of AVRT usually triggered by?

Answer 5

• premature atrial contractions (PAC) or premature ventricular contractions (PVC)
• This leads to tachycardia

Question 6

What is the most common type of AVRT?

Answer 6

Wolff-Parkinson White syndrome (WPW)

Question 7

What accessory pathway does Wolff-Parkinson White syndrome (WPW) form?

Answer 7

bundle of Kent

Question 8

What are the 2 types of AVRT?

Answer 8

• Orthodromic AVRT
• Antidromic AVRT

Question 9

What is Orthodromic AVRT?

Answer 9

The impulse travels down the normal AV pathway and returns up the accessory pathway

Question 10

What is Antidromic AVRT?

Answer 10

The impulse travels down the accessory pathway and returns up the normal AV pathway

Question 11

Which type of AVRT is more common?

Answer 11

Orthodromic AVRT

Question 12

Which type of AVRT is less common?

Answer 12

Antidromic AVRT
but tends to result in wide QRS complex

Question 13

What is the investigation for AVRT?

Answer 13

ECG

Question 14

What is seen on ECG for AVRT?

Answer 14

Slurred delta waves (WPW specific), short PR interval, Tachycardia, and narrow QRS

Question 15

What does AVNRT stand for?

Answer 15

Atrioventricular Nodal Reentrant Tachycardia

Question 16

What is AVNRT?

Answer 16

• is a form of SVT where the reentrant circuit is within the atrioventricular node
• This is one of the most common paroxysmal SVTs

Question 17

What is the pathophysiology for AVNRT?

Answer 17

• In a normal heart, the AV node delays the transmission of the signal before allowing it to pass through to the ventricles
• In AVNRT, a reentrant circuit forms involving pathways within the AV node and the signal circulates, leading to rapid and regular tachycardia

Question 18

What is AVNRT triggered by?

Answer 18

a premature atrial contraction (PAC)

Question 19

What are the 2 types of AVNRT?

Answer 19

• Slow-Fast AVNRT
• Fast-Slow AVNRT

Question 20

What is slow-fast AVNRT?

Answer 20

The impulse travels slowly through the slow pathway and quickly through the fast pathway during the reentrant

Question 21

What is fast-slow AVNRT?

Answer 21

The impulse travels quickly through the slow pathway and slowly through the fast pathway during the reentrant

Question 22

What is the investigation for AVNRT?

Answer 22

ECG

Question 23

What is seen on ECG for AVNRT?

Answer 23

Absence of P waves as they are buried in the QRS Complex

Question 24

What are the symptoms for AVRT and AVNRT?

Answer 24

Palpitations
Tachycardia
Chest discomfort
Dizziness
Syncope

Question 25

What is the first treatment for AVRT and AVNRT in young patients?

Answer 25

first, try Carotid massage (due to the risk of emboli in older patients)

Question 26

Otherwise what is the treatment in AVRT and AVNRT?

Answer 26

work down the list till effective:
- Valsalva manoeuvre
- Adenosine
- Beta blocker or verapamil
If all fails:
- Synchronised DC shock